Stimuli, both internal and external, are detected and lead to a response (A-level only): Practice Questions

• a.The channels actively pump sodium ions out of the neurone to create a resting potential.
• b.The channels open in response to a neurotransmitter binding to a receptor.
• c.The channels close to prevent the loss of potassium ions from the axon.
• d.The channels deform, allowing sodium ions to diffuse into the neurone.

• a.The reflex is voluntary and involves the processing of information in the cerebral cortex.
• b.The impulse bypasses the spinal cord and travels directly from the receptor to the effector muscle.
• c.The speed of the response is slow because it relies on the diffusion of hormones through the blood.
• d.The impulse travels through a sensory neurone, an intermediate neurone in the spinal cord, and a motor neurone.

• a.It delays the electrical impulse to allow the ventricles to fill completely before contracting.
• b.It contains chemoreceptors that detect changes in blood carbon dioxide levels.
• c.It conducts electrical impulses rapidly down the septum to the apex of the heart.
• d.It acts as a pacemaker by sending out regular waves of electrical activity to the atrial walls.

• a.Each rod cell connects to a single bipolar cell for high acuity; multiple cone cells share a bipolar cell for high sensitivity.
• b.Several rod cells share a single bipolar cell, resulting in low acuity; each cone cell connects to its own bipolar cell, resulting in high acuity.
• c.Cone cells are linked in groups to one bipolar cell to ensure spatial summation, which increases acuity in low light.
• d.Both rod and cone cells share bipolar cells, but rod cells have more rhodopsin which increases acuity in bright light.

Write your answer out first, then check it against the worked solution.

Write your answer out first, then check it against the worked solution.